Wednesday, August 19, 2009

Long Distance calling, LRO on the Line

Communicating across great distances has always been a challenge. So when NASA engineers designed the Lunar Reconnaissance Orbiter (LRO), they knew it would need an extraordinary communications system.

Over the next year, the LRO, NASA's diligent robotic scout, will collect more information about the moon's surface and environment than any previous mission. It takes a powerful system to send all of this information more than 238,800 miles back to Earth.

A 13-inch-long tube, called a Traveling Wave Tube Amplifier, is making it possible for scientists to receive massive amounts of images and data from the orbiter at an unusually fast rate. It is the first high data rate K-band transmitter to fly on a NASA spacecraft.

With this new amplifier, LRO can transmit 461 gigabytes of data per day. That's more information than you can find in a four-story library. And it transmits this information at a rate of up to 100 megabytes per second. By comparison, typical high-speed internet service provides about 1 to 3 megabytes per second.L-3 Communications Electron Technologies built the amplifier under the supervision of NASA's Glenn Research Center in Cleveland. The device uses electrodes in a vacuum tube to amplify microwave signals to high power. It's ideal for sending large amounts of data over a long distance because it provides more power and more efficiency than its alternative, the transistor amplifier.

As the orbiter collects information about the moon's geography, climate and environment, the communication system transmits this information to a receiver at a Ka band antenna network at White Sands Test Facility in New Mexico. Scientists are using the data to compile high-resolution, 3D maps of the lunar surface.